1. Field of the Invention
The present invention is directed to a clutch with clearance-recovery devices. In particular, the invention has been developed with reference to a clutch with an automatic-engagement device, provided at the same time with a manual operation device, having recovery devices for the clearances related to wear during the operation of the clutch or else to the machining tolerances of the components at the moment of the assembly of the clutch itself.
2. Description of the Related Art
It is known, in the field of the transmission of motion, the use of multi-disk clutches either of the dry type or of the oil-bath type. This type of clutches in general has a disk pack in which driving disks, integral in rotation with a component of the clutch, typically a bell, which receives motion from a crankshaft connected to the engine of a motor vehicle on which the clutch is installed, and driven disks, integral in rotation with a component of the clutch, typically a hub, which transmits the motion to a driven shaft, typically the primary one of a gear-change, are alternated. The driven disks and the driving disks are made of metal material and the ones or the others, alternatively, are coated with friction material. Finally there are, as it is known, mobile components, in general axially movable, that ensure the engagement of the clutch by compressing the disk pack.
It is known that during use of the clutch the disks are subject to wear due to the relative sliding, in particular during the transients of engagement and disengagement and in situations in which the clutch works as torque-limiting member.
This evidently causes a thinning-out of the friction material present on the disks, and consequently causes a reduction of the total thickness of the disk pack.
This has evidently direct effects on operation of the clutch, both in the case of manually operated clutches, and above all in the case of automatically operated clutches, generally of a centrifugal type. In particular, with the advance of the wear and consequent thinning-out of the disk pack there is in general a variation in the strokes of the mobile components of the clutch of an automatic type that generates altered responses to the inputs of the driver and has a negative effect on the drivability and on the dynamics of the vehicle.
It is likewise known that at the time of the assembly of a clutch it is possible to encounter the presence of clearances caused by deviations of the dimensions of the components themselves with respect to the nominal values in accordance with the tolerances prescribed in the design stage. Also the variation of the clearances of the components causes variation of the strokes of the mobile components of the clutch of an automatic type. This has particular importance in the field of automatically engaged clutches and calls in general for long and economically significant interventions, as will be described hereinafter.
The above-mentioned problems are of particular importance in the field of two-wheeled motor vehicles, in which the characteristics of drivability of a vehicle, as well as the responses thereof to the inputs of the driver, are extremely important both for the performance of the motor vehicle, and for the safety and comfort of the ride.
In particular, in the case of manual control of an automatic clutch, a driver who operates a control lever for performing the normal operations of gear-change or starting from standstill perceives a difference in the response of the clutch due to the wear or to the different assembly clearances thereof, which clearly penalises the drivability of the motorcycle itself.
In the case of automatically operated clutches, in particular of a centrifugal type, the stroke of the mobile components that perform the engagement is proportional to the engine speed of rotation; hence it is evident that in order to engage the clutch it is necessary to reach a higher speed of rotation as the wear increase or for higher values of the assembly clearances, with a strong impact on the characteristics of drivability of the vehicle itself. In addition, also for low values of wear a failure in operation of the clutch itself could occur.
The solutions available in the context of the prior art for automatic clutches envisage in general the insertion of disks of different thicknesses in the disk pack both at the time of assembly and during the use of the clutch to compensate for the wear thereof or the clearances due to the dimensional tolerances. However, installation of the aforesaid disks inevitably entails having to disassemble the clutch. Evidently this is far from convenient and above all it is an intervention that is carried out when the clutch has already in part changed its response to the inputs imparted by the driver of the vehicle; hence, it is not an action that is automatic and transparent to the driver.
The object of the invention is to overcome the problems of the prior art. In particular, the object of the invention is to provide a clutch of an automatic type that is able to maintain characteristics of drivability and of response to the inputs of the driver of the vehicle substantially unchanged with the advance of the wear of the disk pack or owing to the presence of different assembly clearances, compensating in an automatic and way transparent to the driver for the variations in operation due to wear of the disk pack and to the dimensional tolerances of the components.